A longtime outsider in New York State politics has been identified as the link between WikiLeaks and Roger J. Stone Jr., an adviser to Donald J. Trump who appears to have had advance knowledge about hacked emails related to Hillary Clinton’s presidential campaign.

The outsider, Randy Credico, a comedian who has frequently run for office, posted on Twitter on Tuesday that he had received a subpoena requiring him to appear before the House Intelligence Committee next month. The panel is investigating Russian meddling in the 2016campaign.

Mr. Credico could not be reached on Wednesday for comment.

A person familiar with the House efforts said that Mr. Credico had been identified as the intermediary between Mr. Stone and Julian Assange, the founder of WikiLeaks.

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Julian Assange, the founder of WikiLeaks, at the Ecuadorean Embassy in London in May.CreditFacundo Arrizabalaga/European Pressphoto Agency

Mr. Credico, who also hosts a radio show, interviewed Mr. Assange on his program in April, and Mr. Stone, who worked with Mr. Credico on efforts to reform New York’s drug laws, has also appeared on the show.

On a separate occasion, Mr. Credico traveled to London to interview Mr. Assange at the Ecuadorean Embassy, where he has been granted asylum against extradition to Sweden to face questioning on allegations that he sexually abused two young women in 2010.

The question of Russian meddling in the 2016 campaign — including what United States intelligence agencies say was the publication of hacked emails by WikiLeaks — has loomed over Mr. Trump’s presidency, and Mr. Credico’s cameo role in that inquiry has added a surreal note.

Mr. Credico told the Russian news outlet RT, in an interview published online on Tuesday, that he believed the subpoena was “about chilling WikiLeaks, and that starts with intimidating anyone who has met with Julian.”

Mr. Stone is an admirer of Mr. Assange, dating at least to 2011, when he wrote a column supporting Mr. Assange against the allegations of sexual misconduct in Sweden.

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Roger J. Stone Jr. arriving for a closed-door committee hearing in September that examined Russian interference in the 2016 presidential campaign.CreditAl Drago for The New York Times

Asked about the subpoena, Mr. Stone said only: “Randy Credico is a good man. He’s extraordinarily talented. He’s come back from personal adversity often using street theater and satire to illustrate the hypocrisy of our current drug laws.”

(Among his performances: His attendance in 2009 at a meeting of the New York State Senate dressed as the Greek philosopher Diogenes the Cynic. He also served as the political adviser to Al Lewis, the actor who played Grandpa Munster on “The Munsters,” during his campaign for governor in 1998.)

Congressional investigators examining accusations of Russian interference have zeroed in on Mr. Stone and his possible connections to WikiLeaks. Their interest has centered in particular on predictions that Mr. Stone publicly made about damage that Mrs. Clinton’s campaign would face.

Mr. Stone had resisted efforts by congressional investigators to determine the identity of his source about WikiLeaks’ plans. He has previously indicated that he had a source and that the source had simply confirmed what Mr. Assange had publicly tweeted.

Mr. Stone told the House Intelligence Committee that he had merely asked Mr. Credico to confirm that Mr. Assange had told the comedian that he had Clinton-related documents, according to a person familiar with the testimony. Mr. Stone also said that Mr. Credico never mentioned that he knew of the source or content of that material and never indicated whether he had confirmed the information with Mr. Assange.

A version of this article appears in print on , on Page A18 of the New York edition with the headline: Comedian Is Subpoenaed in Inquiry on Russia Meddling. Order Reprints | Today’s Paper | Subscribe